This Thursday July 21, 2011 photo shows young people on the Labour Youth League summer camp on Utoya island, Norway when Norwegian Foreign Minister Jonas Gahr Stoere made a visit. A Norwegian gunman disguised as a police officer beckoned his victims closer before shooting them one by one, claiming at least 84 lives, in a horrific killing spree on an idyllic island teeming with youths that has left this peaceful Nordic nation in mourning. The island tragedy Friday unfolded hours after a massive explosion ripped through a high-rise building housing the prime minister's office, killing seven people. (AP Photo/Scanpix/Vegard Gratt) NORWAY OUT less

This Thursday July 21, 2011 photo shows young people on the Labour Youth League summer camp on Utoya island, Norway when Norwegian Foreign Minister Jonas Gahr Stoere made a visit. A Norwegian gunman disguised ... more

Photo: GrA¯tt, Vegard

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FILE - In this Thursday Oct. 7, 2010 file image shows is a computer generated image of the London 2012 Olympic Park made available by the Olympic Park Legacy Company . The Olympic flame floating down the River Thames. The Olympic rings flashing from Tower Bridge. Fireworks bursting over the London skyline. Hundreds of millions of TV viewers tuning in around the world. In just over a year from now, London will be at the center of global attention when it hosts the opening ceremony of what organizers call the "greatest show on earth" the 2012 Olympics.(AP Photo/Olympic Park Legacy Company, HO) EDITORIAL USE ONLY less

FILE - In this Thursday Oct. 7, 2010 file image shows is a computer generated image of the London 2012 Olympic Park made available by the Olympic Park Legacy Company . The Olympic flame floating down the River ... more

Photo: Olympic Park Legacy Company

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FILE - In this Wednesday, June, 8, 2011 file photo Sebastian Coe Chairman of the London Organizing Committee for the 2012 Olympic games hold up the relay torch as it is unveiled in St Pancras Station below the Olympic rings in central London. The Olympic flame floating down the River Thames. The Olympic rings flashing from Tower Bridge. Fireworks bursting over the London skyline. Hundreds of millions of TV viewers tuning in around the world. In just over a year from now, London will be at the center of global attention when it hosts the opening ceremony of what organizers call the "greatest show on earth" the 2012 Olympics.(AP Photo/Alastair Grant, File) less

FILE - In this Wednesday, June, 8, 2011 file photo Sebastian Coe Chairman of the London Organizing Committee for the 2012 Olympic games hold up the relay torch as it is unveiled in St Pancras Station below the ... more

Photo: Alastair Grant

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FILE - In this taken on Feb. 8, 2011 file photo made available by the London 2012 Olympic Delivery Authority shows an aerial view of the Olympic Stadium .The Olympic flame floating down the River Thames. The Olympic rings flashing from Tower Bridge. Fireworks bursting over the London skyline. Hundreds of millions of TV viewers tuning in around the world. In just over a year from now, London will be at the center of global attention when it hosts the opening ceremony of what organizers call the "greatest show on earth" the 2012 Olympics. (AP Photo/Anthony Charlton) EDITORIAL USE ONLY less

FILE - In this taken on Feb. 8, 2011 file photo made available by the London 2012 Olympic Delivery Authority shows an aerial view of the Olympic Stadium .The Olympic flame floating down the River Thames. The ... more

Photo: Anthony Charlton

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FILE - In this Tuesday, March, 15, 2011 file photo fireworks light up the BT telecom tower in central London to celebrate 500 days to go till the start of the London 2012 Olympic Games.. The Olympic flame floating down the River Thames. The Olympic rings flashing from Tower Bridge. Fireworks bursting over the London skyline. Hundreds of millions of TV viewers tuning in around the world. In just over a year from now, London will be at the center of global attention when it hosts the opening ceremony of what organizers call the "greatest show on earth" the 2012 Olympics. (AP Photo/Alastair Grant, File ) less

FILE - In this Tuesday, March, 15, 2011 file photo fireworks light up the BT telecom tower in central London to celebrate 500 days to go till the start of the London 2012 Olympic Games.. The Olympic flame ... more

Photo: Alastair Grant

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London faces Olympic test

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LONDON -- The London Olympics will open just over a year from now, amid the stunning and historic backdrops of the Houses of Parliament, the Tower of London and Buckingham Palace -- all the monuments that make this city one of the world's most popular destinations.

For that very reason, these games will have a security presence like no other in the face of a constant terrorist threat.

Wednesday marks the one-year countdown to the opening ceremony on July 27, 2012.

For years, London has been bracing for the Olympic onslaught:

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• 10,500 athletes from more than 200 countries.

• 5,000 coaches and team officials.

• 20,000 media personnel.

• hundreds of thousands of visitors.

All for an extravaganza in the most memorable of settings, featuring 26 sports in 32 venues. It's a tall order, even for a place where the flow of tourists never stops. And it's that much more challenging just seven years after a coordinated, deadly attack on London's transit system.

The message from Mayor Boris Johnson: Don't worry. Everything is taken care of.

"With a year to go we can safely say we are ready to welcome the world," he said.

Venue construction is largely completed, tickets are almost sold out, and the government says the games will come in under the 9.298 billion pound ($15 billion) budget. The Olympic Park is changing the face of a previously rundown area of east London.

Athletes will be competing in iconic venues and locations across the capital.

Fans will see Usain Bolt sprinting down the track in a new 80,000-seat Olympic Stadium, beach volleyball players dueling on the sand in Horse Guards Parade, triathletes splashing in Hyde Park's Serpentine, Roger Federer and Rafael Nadal stepping back onto Centre Court at Wimbledon, archers firing their arrows at Lord's cricket ground and showjumpers clearing fences at Greenwich Park.

Underpinning the sports festival will be one of the biggest security operations ever mounted.

Security at the Olympics has been a critical issue ever since the 1972 Munich massacre, even more so after the Sept. 11, 2001 terror attacks. A day after London was awarded the games in 2005, suicide bombers attacked London's transport network, killing 52 people.

The British government is planning for the national terror threat to be "severe" during the Olympics, meaning an attempted attack is highly likely. Security screenings for spectators will be tight and widespread, with airport-style checks at most venues. Away from the competition sites, protecting the Underground subway network and public places will be a major challenge.

"We're already seeing chatter from terror groups regarding the 2012 Games but none of it seems defined at the moment," said a British security official, speaking on condition of anonymity because of the sensitivity of his work. "This is to be expected, though, with an event of this magnitude."